In recent years, an X-ray digital imaging apparatus for performing imaging by using a converter such as a photoelectric transducer for converting light into an electrical signal and thereby using radiation such as X-rays is practically used and spread in accordance with the advancement of semiconductor technology.
Because a digital X-ray imaging apparatus has a sensitivity and image quality superior to those of a conventional film-type imaging apparatus, imaging at lower dose and improvement of diagnosability are possible. Moreover, because an image is stored as digital data, there are advantages that the image can be worked to an image which can be further diagnosed and the image can be easily controlled by performing various image processings after imaging the image. Moreover, by effectively using the advantage of digital data and thereby using a network to transfer image data, it is possible to make the image diagnosis in a hospital efficient and remote diagnosis efficient or realize new medical care service.
By using a digital X-ray imaging apparatus having these advantages, it is possible to provide medical care service higher than the case of a convention X-ray imaging apparatus in quality such as improvement of diagnostic accuracy, making diagnosis efficient, or development to new medical care service.
The above digital X-ray imaging apparatus is disclosed in U.S. Pat. No. 6,965,111, for example.
As a photoelectric conversion element used for the pixel of a two-dimensional area sensor of the X-ray imaging apparatus disclosed in U.S. Pat. No. 6,965,111, an MIS-type conversion element such as an MIS (Metal-Insulator-Semiconductor)-type photoelectric conversion element is mainly used and as a switching device, a TFT (Thin Film Transistor) is mainly used. The two-dimensional area sensor using the MIS-type photoelectric conversion element performs the operation for initializing an MIS-type photoelectric conversion element referred to as the refresh operation disclosed in U.S. Pat. No. 6,075,256.